1. Field of the Invention
The present invention relates to a method for manufacturing a liquid crystal display device, and more particularly, to a method for manufacturing a bottom substrate of a liquid crystal display device.
2. Description of Related Art
In comparison with the cathode ray tube (CRT) monitors, the liquid crystal display device has the advantages of low power consumption, compact size, and non-radiation. However, the price of the thin film transistor liquid crystal display device (TFT-LCD) is relatively high. In particular, the manufacturing cost of the thin film transistor liquid crystal display device cannot to be further lowered, as the quantity of masks used in the photolithographic process for forming the transistor array of the liquid crystal display device cannot be reduced effectively.
The conventional method for manufacturing a thin film transistor array substrate uses five masks in its photolithographic processes. The first mask is used to define the first metal layer, and thereby forms the scan lines and the gate electrode of the thin film transistor. The second mask defines the channel layer and the ohmic contact layer of the thin film transistor. The third mask is used to pattern the second metal layer in order to form the data lines and the source and the drain electrodes of the thin film transistor. The fourth mask patterns the passivation layer. As for the fifth mask, it patterns the transparent electrode layer to form the pixel electrode.
As the liquid crystal display device tends to develop a thin film transistor liquid crystal display device having a larger display size, there are inevitably many problems, such as reduction in yield and capacity, to be solved. Therefore, if the quantity of masks used during the manufacturing of the thin film transistor can be reduced, i.e. reducing the quantity of the exposure processes, the manufacturing time can be reduced, the capacity can thus be increased, and the manufacturing cost is thereby lowered.
In addition, the photolithographic process used for the manufacturing of thin film transistor liquid crystal display device is quite expensive. Thus, reducing the photolithographic process can essentially lower the cost.
Therefore, it is desirable to provide an improved manufacturing method to mitigate and/or obviate the aforementioned problems.